1. Field of the Invention
This invention relates in general to obstruction sensors for closure operators as, for example, electro-mechanically operated garage doors.
2. Description of the Prior Art
Residential garage door openers commonly use an obstruction sensing system for limiting the output torque of the electro-mechanical drive. These prior art systems generally are insensitive to obstructions which occur when the door is in the last few feet of its closing travel due to the geometry of the forces involved. Thus, such prior art systems at times are incapable of reversing the door when obstructions were encountered during the last few feet of the door closing travel.